Odd vs even flight numbers
Having traveled internationally a lot over the last 20 years, I've noticed that the flights from the airline's home country are usually odd numbered, while flights to home country are usually even numbered. I have not flown enough domestically within any one country to notice any patterns though.
Are there specific rules (probably unwritten) or other things that dictate odd vs even flight numbers?
Best Answer
There is no industry standard, written or otherwise, for the way that flight numbers are allocated. Some airlines will have published or unpublished standards for how flight numbers are allocated - sometimes these will be strictly followed, whilst other times they will only be loosely followed.
As a few examples...
Australian airline Qantas uses ranges of flight numbers to designate a number of things, but the most important of these is that flight QF1 to QF399 are international flights, whilst QF400 and above are domestic flights (not including codeshare flights which start around QF2600).
Qantas DOES follow the odd/even pattern you described for international flights, with odd flight numbers being used for flights departing Australia, and even flight numbers being used for flights arriving in Australia. eg, QF7 from Sydney, Australia to Dallas, USA is an international flight (<400), departing Australia (odd).
For domestic flights, South/West bound flights have odd numbers, whilst North/East flights have even numbers. Some ranges can also designate the type of aircraft normally flying on a route. eg, QF1501 is a south-bound route that would normally be flown by a QantasLink Boeing 717!
Germany's Lufthansa Airline goes the other way when it comes to even/odd flights - even numbers designate a flight out of Germany, whilst odd designates a flight to Germany. Lufthansa flight numbers also often designate the destination of the flight. eg, flight numbers LH400-499 are flights to North America. Thus LH458 is a flight to (even) North America (4xx) - in fact it's from Munich to San Francisco.
For domestic flights, Lufthansa flights out of Frankfurt airport always appear to be even numbers - although I'm not sure if that is always the case or just the vast majority of the time.
United Airlines does not follow an even/odd flights number rule. For example, the two UA flight from San Francisco to London Heathrow today are UA901 and UA948 - one odd, the other even! United did historically follow a geographic model for international flight numbers, with UA8xx being flights to Asia Pacific/Oceania, UA9xx being flights to Europe, etc, and whilst many flights do still followed these conventions, many do not. For example, UA1 to Singapore, and UA98 to Melbourne, Australia.
Some airlines (especially those that use odd/even numbers for direction) will follow a "sequential" numbering scheme where the return flight number is one higher than the outbound flight, whilst others will not. For example, the return flight to LH458 mentioned above is indeed LH459 (SFO-MUC). Same for UA2 (SIN-SFO) and UA99 (MEL-LAX). However again this is not strictly followed by all airlines - the return flights for United's two London flights mentioned above (UA901 and UA948) are UA900 and UA949 which are sequential but in opposite directions to each other, whilst the return flight for United's UA863 (SFO-SYD) is UA870!
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Is the flight number the plane number?
Officially the term 'flight number' refers to the numeric part (up to four digits) of a flight code. For example, in the flight codes BA2490 and BA2491A, "2490" and "2491" are flight numbers. Even within the airline and airport industry, it is common to use the colloquial term rather than the official term.Are flight numbers unique?
There is nothing anywhere to say that the airline won't change the flight number or reuse the same flight number to connect different destinations. Case in point: United flight 237 contains 2 different segments flown by 2 different aircraft today so in essence you can look at it as 2 different flights.Do different flight numbers mean different planes?
Even flight numbers are typically assigned to north and eastbound flights while south and westbound flights end in odd numbers. Airlines typically assign the return flight number as one digit higher than the outbound flight. Generally, the lower the flight number, the more important that route is to the airline.Can two flight numbers be the same?
Yes, the same flight number can be used to refer to multiple flights active at the same time. This happens fairly regularly if a flight is heavily delayed. The previous days flight may still be active the same time as the current days flight takes off.EVEN Number Kits vs. ODD Number Kits!
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